Switching power supply for generating a ringing voltage

Abstract

An apparatus and method for providing a ringing voltage to a communication device such as a telephone or a modem. Typically, communication devices are coupled to a ringing voltage providing telephone network, such as a Plain Old Telephone Service (POTS) network. The POTS network generally provides the necessary ringing voltages to the communication device. However, in other telephone networks, such as a PBX system, ringing voltages are not provided by the telephone network. The apparatus provides ringing voltages to the communication devices coupled to the non-ringing voltage providing telephone networks. The apparatus includes a switching regulator that provides the necessary ringing voltages to an indicator such as a bell or other output indicator.

I claim:  
     
       1. A modem adapted for use with a non-ringing voltage producing (n-RVP) telephone network, comprising: 
       an analog front end (AFE) circuitry adapted to perform communication functions;  
       a RING conductor coupled to the AFE circuitry;  
       a TIP conductor coupled to the AFE circuitry; and  
       a feedback-controlled ringing voltage source, coupled to the RING conductor and the TIP conductor, the ringing voltage source adapted to generate a ringing voltage on the RING conductor and the TIP conductor responsive to a ring control signal from the n-RVP telephone network.  
     
     
       2. The modem of  claim 1 , the ringing voltage source comprising: 
       a ring control signal line, couplable to the n-RVP telephone network and adapted to receive the ring control signal;  
       a switching regulator adapted to generate an output signal on an output signal line coupled to the RING conductor and the TIP conductor; and  
       a feedback circuit, coupled to the switching regulator and the ring control signal line,  
       wherein the switching regulator is adapted to place a ringing voltage on the output signal line responsive to feedback from the ring control signal and the output signal.  
     
     
       3. The modem of  claim 2 , wherein the feedback circuit is adapted to modulate the output signal on the output signal line responsive to the ring control signal. 
     
     
       4. The modem of  claim 1 , wherein the ring control signal is an AC signal. 
     
     
       5. The modem of  claim 1 , further comprising: 
       a DC input voltage, coupled to an input of the switching regulator and coupled to the RING conductor and the TIP conductor.  
     
     
       6. The modem of  claim 1 , the feedback circuit comprising: 
       an operational amplifier, an output of the operational amplifier coupled to a feedback input of the switching regulator, a first input of the operational amplifier coupled to the ring control signal line, and a second input of the operational amplifier coupled to the RING conductor and the TIP conductor.  
     
     
       7. The modem of  claim 1 , wherein the n-RVP telephone network is a private branch exchange.